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Distinct binding specificities and functions of higher eukaryotic polypyrimidine tract-binding proteins
R Singh1, J Valcárcel, M R Green
1Howard Hughes Medical Institute, Program in Molecular Medicine, University of Massachusetts Medical Center, Worcester 01605, USA.
Science (New York, N.Y.)
|May 26, 1995
Summary
Polypyrimidine tract-binding protein (PTB) and other splicing factors recognize distinct sequences near splice sites. PTB selectively represses alternative splicing by binding to specific sites, influencing gene expression.
Area of Science:
- Molecular Biology
- Genetics
- RNA Splicing
Background:
- The polypyrimidine tract (Py-tract) near the 3' splice site is crucial for pre-mRNA splicing in eukaryotes.
- Several proteins, including U2AF65, Sex-lethal (Sxl), and polypyrimidine tract-binding protein (PTB), interact with the Py-tract.
- The precise function and sequence preferences of PTB in splicing regulation were previously unknown.
Purpose of the Study:
- To investigate the distinct sequence preferences of splicing factors U2AF65, Sxl, and PTB.
- To elucidate the role of PTB in alternative splicing regulation.
Main Methods:
- Iterative in vitro genetic selection was employed to determine protein-specific sequence preferences.
- Analysis of natural metazoan Py-tracts and alternatively spliced pre-mRNAs.
Main Results:
- U2AF65 binds to uridine-rich sequences similar to natural metazoan Py-tracts.
- Sxl recognizes a highly specific consensus sequence, explaining its regulatory roles.
- PTB binds to a distinct consensus sequence found in negatively regulated alternatively spliced pre-mRNAs.
- PTB was shown to selectively repress 3' splice sites containing its binding site.
Conclusions:
- Splicing factors exhibit distinct sequence specificities for Py-tract recognition.
- PTB plays a significant role in alternative splicing by repressing specific 3' splice sites.
- Understanding these interactions provides insights into the regulation of gene expression through alternative splicing.
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